In order to harvest alignments of roots aligned along longitudinal rows, as they mature, in particular in order to harvest sugar beets, a known type of machine, presented in particular in document EP-B1-1772050, includes an assembly disposed at the front of a powered tractor, comprising successively starting from the front, guide wheels, a unit for stripping most of the leaves, a horizontal cutting unit of the head of the beets so as to eliminate the remaining leaves and scalp the beet, and a harvesting unit which digs the ground beneath the beets so as to extract them, eliminate the soil, and lift them towards a storage means.
In the remainder of this document, the term beet will encompass all types of roots which may be harvested with these machines.
The unit for cutting the head of the beets includes for each row a horizontal cutting blade, comprising just in the front a vertical guide or cam, presenting parallel bars forming a curve rising at the front so as to slide over the top of the beet to be cut, which is terminated rearwards slightly above the blade.
For each row of beets, the cutting unit is mounted on a substantially balanced support which enables a rise and a descent of the guide bearing successively on the top of each of the beets. In this manner, the blade following behind being adjusted slightly beneath this guide, cuts the beet horizontally just beneath its top.
The harvesting unit following this cutting unit also includes a height positioning related to the level of the cutting blade, so as to dig the soil according to a predefined height relative to the cutting level. Thus, an optimization of the soil digging depth is achieved, for beets including a standard height.
Nonetheless, this type of automatic adjustment of the level of the harvesting unit is not optimized in all cases. In particular, if the beets are smaller with a reduced height, or in the case of an absence of beets, the ground will be dug too deep or uselessly, with a very high fuel consumption to power the machine. Conversely, if the beets are bigger with a more significant height, there will then be the risk of damaging their bases and loose a portion of the harvest because we would have not dug deep enough.